Ceramic honeycomb structure and its production method

Abstract

A ceramic honeycomb structure having pluralities of flow paths partitioned by porous cell walls; (a) the cell walls having porosity of 50-60%; and (b) in a pore diameter distribution in the cell walls measured by mercury porosimetry, (i) pore diameters at cumulative pore volumes corresponding to particular percentages of the total pore volume being within specific ranges and having specific relationships; and (ii) the difference between a logarithm of the pore diameter at a cumulative pore volume corresponding to 20% of the total pore volume and a logarithm of the pore diameter at 80% being 0.39 or less, and its production method.

What is claimed is: 
     
       1. A ceramic honeycomb structure having pluralities of flow paths partitioned by porous cell walls,
 (a) said cell walls having porosity of 50-60%; and 
 (b) in a pore diameter distribution in said cell walls measured by mercury porosimetry, 
 (i) a pore diameter d5 at a cumulative pore volume corresponding to 5% of the total pore volume being 22 μm or more and less than 55 μm, 
 a pore diameter d10 at 10% being 15-35 μm, 
 a pore diameter (median pore diameter) d50 at 50% being 10-20 μm, 
 a pore diameter d85 at 85% being 5-9 μm, 
 a pore diameter d90 at 90% being 3-8 μm, 
 a pore diameter d98 at 98% being 2.5 μm or less, 
 (d10−d90)/d50 being 1.3-1.8, 
 (d50−d90)/d50 being 0.45-0.75, and 
 (d10−d50)/d50 being 0.75-1.1; and 
 (ii) σ[=log d20−log d80] being 0.39 or less, wherein σ represents the difference between a logarithm of the pore diameter d20 at a cumulative pore volume corresponding to 20% of the total pore volume and a logarithm of the pore diameter d80 at 80%. 
 
     
     
       2. The ceramic honeycomb structure according to  claim 1 , wherein a pore diameter d2 at a cumulative pore volume corresponding to 2% of the total pore volume is 75-250 μm, and the volume of pores of 20 μm or more is 0.12 cm 3 /g or less. 
     
     
       3. The ceramic honeycomb structure according to  claim 1 , wherein said porosity is 52-60%. 
     
     
       4. The ceramic honeycomb structure according to  claim 1 , wherein said median pore diameter d50 is 10-18 μm. 
     
     
       5. The ceramic honeycomb structure according to  claim 1 , wherein said σ is 0.3 or less.